Model (with has many / belongs to) to json

i have a model called Event which has many participants.
The Participant i defined as, belongs to Event.

Now i want to export my Event as a Json.
But when i do Ext.JSON.encode(event.getData()), i get the following error:
RangeError: Maximum call stack size exceeded.

I think the problem here is that when i look at the event.getData() object this contains a participants variable, which itself contains an event variable.
And ofcourse that event variable contains a participants... etc.

So this goes into an infinite loop.

Now my question here is, what is the best way to describe my models?
What associations should i use?